Correction of flow metering coefficients by using multi-dimensional non-linear curve fitting

Flow disturbances can significantly affect flow metering because the downstream flow of flow disturbances can become unstable and asymmetric, thus resulting in measurement errors in the flow meter. A clamp-on type ultrasonic flow meter is an example of a flow meter that is susceptible to flow disturbances given its diametrical configuration of ultrasonic paths. Several flow rate correction formulas have been suggested to mitigate the effect of flow disturbance for improved flow metering. As a novel method, a multi-dimensional non-linear correction formula is suggested to overcome limitations in flow metering that are attributed to the non-linearity of flow disturbances. The non-linear correction formula comprises n-th order polynomials with multiple variables. To validate the usefulness of the non-linear correction formula, the standard error of estimate (SEE) is introduced. Four types of flow configurations, namely, downstream of a contraction pipe, an expansion pipe, a single elbow joint, and a tee joint, are used to show the effect of the non-linear correction formula. The expanded uncertainty based on the SEE indicates estimated values of 1.29%, 11.14%, 1.07%, and 6.31% for the four upstream flow configurations, respectively. Thus, the effect of the non-linear correction formula is limited according to the upstream flow conditions. In the downstream flow of the contraction pipe and of the single elbow joint, the non-linear correction formula not only harmonizes the distribution of the flow rate deviations but also removes the biases of flow rate deviations with respect to the flow velocity, the installation location, and the diameter ratio.     

挤压丝锥结构参数对内螺纹冷挤压成形过程扭矩的影响

将内螺纹冷挤压成形过程分为三个主要阶段,并将成形过程扭矩最大值作为标定整个成形过程扭矩的指标,得到其理论计算公式,并在得到试验验证的基础上,研究分析了挤压丝锥各结构参数(挤压锥部长度、校正部长度、挤压锥角、铲背量、棱齿数、大径及螺距)对其成形过程扭矩的影响规律。     

齿轮内啮合传动的重合度及载荷修正系数的计算(Ⅱ)--载荷修正系数数据表

在获得齿轮内啮合传动的齿侧间隙计算公式以后，结合齿对刚度的计算公式，推导出齿轮内啮合传动的加载重合度及载荷修正系数。通过对具有不同模数、齿数、齿数差、变位系数及载荷的齿轮内啮合传动模型的计算，发现载荷及齿数(传动比)的变化对载荷修正系数的影响较大，齿数差及变位系数的变化对载荷修正系数的影响较小，齿轮的精度对载荷修正系数的影响最大。载荷修正系数在0．30至1．00之间变化。     

轴向磁化双永磁环悬浮轴承静态磁力的研究

永磁悬浮轴承由于结构简单且不需要复杂的位置控制系统而具有相当的应用价值。基于永磁材料的线性退磁曲线,通过对双永磁环的磁路分析,利用间隙磁导的拟合计算公式,采用虚功原理法得到双永磁环轴向静态磁力的解析模型,该解析模型可以计算不同内外径的双永磁环悬浮轴承的轴向静态承载力,并设计了测量双永磁环间隙与磁力关系的实验装置,实验结果表明,永磁环磁力解析模型的计算值和实测值吻合较好,该方法能较好的计算出双永磁环悬浮轴承的静态承载力。     

共振扫描显微成像中的图像畸变校正

设计了一种校正算法用于校正双光子荧光显微镜等高速扫描成像系统中共振振镜扫描导致的图像畸变。首先对共振振镜的扫描运动建立模型,推导出非线性扫描的运动公式,进而得到图像畸变公式;然后对一块朗奇光栅样品扫描成像,设计了多峰高斯拟合算法得到光栅所有条纹的宽度变化并通过最小二乘法将条纹宽度数据拟合成一条畸变曲线;最后利用畸变曲线对图像进行校正。结果表明:采用提出的校正算法可使系统最大畸变减小到传统正弦校正方法的1/3,相对畸变减小到1/5,校正效果比传统的正弦校正法提高了2倍。由于提出的曲线拟合校正算法不用增加额外的光路,且不需要切割边缘图像,故显示了极好的图像使用效率和校正效果。     

表面热电离同位素稀释质谱法的计算及质量分馏效应校正

表面热电离同位素稀释质谱法(ID-TIMS)是国际公认的基准方法之一。本文以稀释分析锶同位素为例,详细介绍了其计算和推导过程,提出基于指数近似模式的稀释分析同位素分馏校正的方法。该方法适用于校正含有两对参考比值的元素静态多接收稀释分析同位素比值的质量分馏,与指数校正方法和对数校正方法相比,计算过程更简单。还讨论了稀释剂同位素比值准确度对稀释分析同位素比值的影响及其质量分馏的校正方法,通过数学迭代计算质量分馏系数,得到稀释剂测量的质量分馏系数和准确的同位素比值。采用建立的质量分馏校正方法稀释分析NBS987,结果表明,在误差范围内与其参考值（⁸⁷Sr/⁸⁶Sr=0.710237±8（1σ））一致。     

聚合物熔体微尺度剪切黏度测量方法与黏度模型

研究微尺度效应下聚合物熔体黏度时,发现不同入口修正方法获得的剪切黏度随特征尺寸变化的规律不同,这对于聚合物微成型理论和技术尤为重要。采用直径分别为1 000μm、500μm、350μm的毛细管口模,在相同试验条件下分别用零口模法和Bagley法两种入口修正方法,研究高密度聚乙烯(High density polyethylene,HDPE)、短链支化的聚丙烯(Polypropylene,PP)、聚甲基丙烯酸甲脂(Polymethylmethacrylate,PMMA)和聚苯乙烯(Polystyrene,PS)四种材料的剪切黏度变化规律。结果发现,两种方法获得的PMMA和PS黏度随口模直径变化的规律相反,指出传统入口修正方法在测量微尺度黏度时存在局限。基于入口收敛流动特征,提出一种考虑微尺度效应下压力影响的测量方法,并用该方法给出四种材料剪切黏度随口模直径变化的真实规律。试验剪切速度范围内,四种材料剪切黏度均随口模直径的减小而减小,平均变化幅度为9.9%～38.3%,并从分子结构角度揭示四种材料黏度变化程度不同的机理。基于黏度变化规律,采用唯象性方法建立适用于宏—微观尺度下的黏度模型。试验结果表明该模型的理论预测结果与试验结果平均误差小于3.7%,验证了模型的正确性和有效性。     

天顶摄影仪轴系误差对垂线偏差测量精度的影响及其修正方法

由于机械加工精度和常平架的调平精度有限,天顶摄影仪的视轴、垂直旋转轴与铅垂线总是存在不一致,导致测量精度与理论精度存在很大的偏差.为了提高垂线偏差测量系统的精度,根据天顶摄影仪的测量原理,定性、定量地分析了各种轴系误差对垂线偏差测量精度的影响,提出了相应的修正方案,推出了修正公式和修正后的误差公式,同时还分析了由于轴系不一致引起的恒星影像偏差及其影响.最后,考虑实际的工艺水平,确定了系统的各种参数,通过仿真、模拟计算得出修正后的系统测量误差为0.4285″.     

基于有限元的双道金属O形环压紧力分析*

双道金属O形环是反应堆压力容器常用的密封结构。为研究在双道密封下金属O形环所需最小压紧力的计算公式,利用ANSYS有限元软件,建立金属O形环二维轴对称模型,求出在相同压缩率下单道与双道密封压紧力值。建立双道密封压紧力计算的修正公式,通过比较双道密封压紧力有限元值和理论值,得出双道密封的修正系数。结果表明：密封环中心圆直径一定,在相同压缩率下,单道密封环所受压紧力要小于双道的第一道密封环压紧力。当第一道密封修正系数取1.021,第二道密封修正系数取1.028时,修正公式计算的最小压紧力值与有限元计算值吻合。     

水下绳锯机串珠绳张力检测装置的动态特性研究

介绍了水下绳锯机串珠绳张力检测装置组成和工作原理.对检测装置中导向绳轮的动力学特性进行了理论分析,推导出了张力检测装置静态标定时的理论修正公式,试验结果与理论修正结果基本吻合,从而证明了理论修正公式的合理性.应用此公式对张力检测装置进行现场静态标定,海上试验表明,张力检测装置达到了预期设计要求,绳锯机能安全高效的工作.     

Stylus contact time during measurement—An effective factor in accuracy

An experimental study was carried out to determine formulae showing the effect of instantaneous and time local deformation at the point of contact between stylus and measured surface on the precision and accuracy of both measuring standard slip gauges and brass workpieces.Such formulae are useful in practice as new correction functions for the precision and accuracy of measurement. Using styli with spherically ended tips of various diameters as used in practice a wide range of measuring forces, different surface finishes of brass workpieces and time of measuring were investigated.     

Control of corrosion-erosion of tube inlets of shell and tube heat exchangers

Earlier investigations showed that excessive corrosion of the first few diameters of standard shell and tube heat exchangers is the consequence of an unfavourable flow pattern in the inlet channel. Flow correction devices were incorporated in a model shell and tube heat exchanger to alter the existing flow pattern to give an axial flow into the tubes in order to reduce tube inlet corrosion. The resulting modified flow characteristics were studied by flow visualization and velocity distribution measurements. Recommendations regarding optimum dimensions and positioning of the various flow correction devices are made.     

基于进化算法的液体动力润滑轴承优化设计

采用Matlab语言,分别运用改进型粒子群算法和基本粒子群算法,在最大限度满足液体动力润滑径向滑动轴承的承载量系数值,以达到滑动轴承承载能力的条件下,对内燃机径向滑动轴承进行了优化设计,计算机仿真结果表明:采用改进型粒子群算法优化的轴承孔直径、轴径直径、轴承宽度、承载量系数等优化参数效果最好,符合实际工艺要求,且滑动轴承承载能力最强。改进型粒子群算法优化结果明显优于基本粒子群算法的优化结果,从而表明了改进型粒子群算法应用于内燃机问题的优化求解切实可行。     

斜接管道结构在内压作用下塑性极限载荷的有限元分析方法研究

采用有限元方法,建立了斜接管压力容器结构在内压作用下的数值模型,并将不同载荷下管道的热点应力分布与现有文献实验结果进行了比较,两者吻合较好,验证了该计算方法的可靠性。对于正交接管利用两倍弹性斜率、切线交点和零曲率极限载荷准则获得斜接管道失效的极限内压;并将正交接管的极限内压与Cloud以最大有效应力达到屈服时对应的理论上极限内压值进行比较,结果表明：两倍弹性斜率与切线交点极限载荷准则在预测极限内压时偏于保守,零曲率准则对确定斜接管压力容器的极限载荷比较恰当。然后利用零曲率准则确定斜接管压力容器的极限载荷,采用控制单变量变化的方法,分别分析了接管中心线与简体中心的夹角、接管与筒体直径之比和筒体厚度与直径之比对极限载荷的影响,最后综合考虑这些因素的影响,得出了斜接管压力容器极限载荷的近似计算式。提供的分析方法为压力容器的设计及安全性评定提供了一种新途径。     

含肩部减薄缺陷三通受内压时的塑性极限载荷分析与研究

利用ANSYS有限元分析软件对含肩部减薄缺陷焊制三通进行塑性极限内压的计算和分析，确定了影响三通塑性极限内压的主要因素，建立了覆盖常用三通几何特征参量和肩部三维减薄缺陷大小变化范围的塑性极限内压有限元解数据库，并拟合得到形式简单且具有较高精度的塑性极限内压工程估算公式。     

吸入室直径对液气射流泵流场特性影响的数值模拟

为了全面分析液气射流泵内部结构对液气射流泵吸气性能的影响,以提高液气射流泵整体吸气性能。利用Fluent软件对不同吸入室直径下液气射流泵内部流场进行了三维数值模拟,获得了液气射流泵内部压力场和速度场分布以及轴心静压曲线,并拟合出压力比、流量比、效率与不同吸入室直径的关系曲线。对比分析表明,吸入室直径的大小会对液气射流泵内部压力、速度及吸气效率产生很大影响。射流泵其他结构一定时,吸入室直径大小存在最优值或者最优范围,使得液气射流泵的吸气性能最佳。     

A Film Thickness Correction Formula for Double-Newtonian Shear-Thinning in Rolling EHL Circular Contacts

Lubricants which contain a polymeric thickener will often display a second Newtonian plateau in measured flow curves. Like other manifestations of shear-dependent viscosity, this shear response will lead to an inaccurate prediction when the classical film-thickness formulas are employed. A correction formula has been developed from numerical experiments for a range of parameters of the double-Newtonian modified Carreau equation. The parameters of this shear-thinning model were selected from measurements for real lubricants obtained in Couette viscometers and a capillary viscometer. In addition, a full EHL film thickness formula has been derived from the same numerical experiments. The correction formula and the full formula were successfully validated using published film thickness data and published viscosity data for an EHL reference liquid, a polymer solution. Clearly, viscometer measurements of shear-dependent viscosity which contain the inflection leading to the second Newtonian are essential for a film-thickness calculation when a high-molecular-weight component of the lubricant is present.     

Experimental study on bubble size distribution of subcooled flow boiling in cylinder head of internal combustion engines

Subcooled flow boiling is becoming an efficient and widely used heat transfer approach in internal combustion engine cooling systems. Bubble evolution behaviors are crucial for understanding the mechanism of subcooled flow boiling. In this study, a diesel engine test platform equipped with endoscopic high-speed photography system was built to investigate the characteristics of boiling bubble. Under various inlet liquid subcoolings and flow rates, the mean bubble diameters and bubble size distributions were measured and analyzed based on the image processing techniques. Most of the bubbles approximated the spherical and ellipsoidal shapes. The bubble size was distributed between 1 and 2.5 mm, and the bubble diameters increased with the decrease of the inlet subcooling and flow rate. The flow rate had a more significant effect on the formation of large boiling bubbles.

     

气动系统内部结露的机理研究

以容积固定的气动充放系统为研究对象,利用空气动力学、热力学、凝结理论和气悬浮体理论等对内部结露进行了研究,揭示了内部结露的机理。并利用模糊数学的思想。综合各种影响因素给出了系统发生结露可能性的公式。     

高压环境下温度传感器矫正系统研制及应用

现有的热敏电阻温度传感器在高气压环境下使用时大都会出现温度测试值不准的问题,对同样温度的热源在常压与高压下进行温度测试的结果偏差较大,表明该类温度传感器在高压环境下使用存在较大的偏差。本研究设计了一套高压下使用的温度矫正系统来解决高压下温度测试不准的问题,通过加压舱内设置水银温度计与热敏电阻温度传感器的对比测试,得出测试温度与矫正温度的数据,并通过数据拟合的方式得出矫正公式,为常用温度传感器在高压下的矫正使用提供了合理的技术支持。